Observation of electroweak production of two jets in association with an isolated photon and missing transverse momentum, and search for a Higgs boson decaying into invisible particles at 13 \text {TeV}TeV with the ATLAS detector

ALONSO FRANCISCO, ET. AL. (ATLAS COLLABORATION)

EUROPEAN PHYSICAL JOURNAL C - PARTICLES AND FIELDS

SPRINGER

Lugar: Berlin; Año: 2022

1434-6044

This paper presents a measurement of the electroweak production of two jets in association with a Zγ pair, with the Z boson decaying into two neutrinos. It also presents a search for invisible or partially invisible decays of a Higgs boson with a mass of 125 \text {GeV}GeV produced through vector-boson fusion with a photon in the final state. These results use data from LHC proton?proton collisions at \sqrt{s} = 13 TeV collected with the ATLAS detector and corresponding to an integrated luminosity of 139 fb^{-1}. The event signature, shared by all benchmark processes considered for the measurements and searches, is characterized by a significant amount of unbalanced transverse momentum and a photon in the final state, in addition to a pair of forward jets. Electroweak Zγ production in association with two jets is observed in this final state with a significance of 5.2 (5.1 expected) standard deviations. The measured fiducial cross-section for this process is 1.31±0.29 fb. An observed (expected) upper limit of 0.37 (0.34^{+0.15}_{-0.10}) at 95% confidence level is set on the branching ratio of a 125 GeV Higgs boson to invisible particles, assuming the Standard Model production cross-section. The signature is also interpreted in the context of decays of a Higgs boson into a photon and a dark photon. An observed (expected) 95% CL upper limit on the branching ratio for this decay is set at 0.018 (0.017^{+0.007}_{-0.005}), assuming the Standard Model production cross-section for a 125 GeV Higgs boson.